Systems Biology – Lesson 9

In lesson 9, our first lesson of the week, we circled back to osmosis, a concept students learned about early in the school year.  We connected the theme of “Water Follows Salt” with the reality that cell membranes contain pores and channels that regulate the flow of everything across the cell membrane.  We discussed the vocabulary of osmosis in the context of blood, recognizing that blood cells in plasma (isotonic) behave much differently than blood cells in water (hypotonic) or in saltwater (hypertonic).  We then thought about how salmon might be able to transition from freshwater to saltwater during their life cycle.  By connecting pore protein expression (via the Central Dogma) with evolution, students now have the foundation necessary to explain how salmon can hatch from an egg fertilized in a freshwater stream, migrate through the brackish waters of an estuary out into the Puget Sound, travel for years in the salty Pacific Ocean, and eventually find their way back to the steam from which they were born to complete their life cycle.   We wrapped up with a video about ice cave exploration, in which the concept of extremophiles was presented.  Students then transitioned to Work Time where they read an article and answered questions about extremophiles.